Objective To evaluate procalcitonin (Pct), white blood cell(WBC), neutrophil percentage(N), and high sensitivity C-reactive protein(hs-CRP) in the diagnosis of febrile patients with lung cancer. Methods A total of 113 febrile patients with lung cancer were enrolled in the study, who were treated in the Department of Oncology of Shijingshan Hospital. Based on the causes of fever, the patients were divided into fever-induced-by-inflammation (FIBI) group (n=71) and fever-induced-by-tumor (FIBT) group (n=42). The former was further divided into the sepsis subgroup (28 cases) and non-sepsis subgroup (43 cases). Also enrolled in the study as control group were 20 patients with lung cancer without fever and inflammation, who were treated during the same period. Blood samples were obtained for Pct, WBC, N and hs-CRP after their admission to the hospital and cure of infection. SPSS statistics 16.0 was used for data analysis. Spearman analysis was performed to investigate the relationships between variables. Receiver operating characteristic (ROC) curve was adopted to analyze the value of Pct in diagnosis of infection in febrile patients with lung cancer. Results Pct was significantly higher in the FIBI group than both the FIBT group (Z=5.101, P<0.001) and the control group(Z=5.169, P<0.001), and it was also significantly higher in non-sepsis group than in the FIBT group (Z=4.334, P<0.001). Pct was positively correlated with WBC (r=0.352, P=0.003), N (r=0.385, P=0.001), and hs-CRP (r=0.427, P=0.002) in the FIBI group. Using FIBT group as control, area under ROC curve (AUC) of Pct for the FIBI group was 0.907(95％CI 0.833-0.982), with the optimal cutoff value being 0.53 ng/ml, a sensitivity of 0.833 and a specificity of 0.857. Conclusion Pct is valuable in the differential diagnosis of fever induced by tumor and inflammation in the patients with lung cancer.